[FEATURE] equivalent to sklearn discovery module

[DCoupry]

sklego should have an equivalent to: sklearn.utils.discovery, a module that stores methods such as:

• all_estimators(filter=typing.Literal["classifier","transformer", etc...])
• all_displays
• all_functions...

This greatly simplifies the automatic use of the library in the context of auto-ML in particular. If interested, I can start work on a PR.